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This is an FDG PET TT performed on a 48-year-old female

0:06

with a history of endometrial carcinoma

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that had undergone, uh, surgery

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and, uh, was on chemotherapy induction.

0:17

I want to draw your attention to the

0:22

bone marrow uptake.

0:23

As you can see, there's intense bone marrow uptake

0:26

that is diffused and involves both the axial as well

0:30

as the appendicular skeleton

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and, uh, appears to be very homogeneous.

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Also, if we compare the degree

0:37

of uptake in the bone marrow compared to the sub tissues,

0:42

the uptake in the bone marrow is very high,

0:44

giving us a good differentiation.

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This is a common pattern in patients

0:51

that are undergoing chemotherapy

0:53

because prior to the chemotherapy,

0:55

they receive certain agents that are called

0:59

granulocyte colony stimulating factors

1:03

to stimulate the bone marrow,

1:04

and so the bone marrow becomes more active

1:08

and that is reflected in an o increase use of glucose

1:13

and we see it as increase.

1:15

Uh, FDG uptake, like in this case,

1:19

on the top row we have the same patient, uh, that came back

1:23

but had not had the agent given

1:28

prior to the pit.

1:29

And so the bone marrow is seen normally

1:35

compared to the prior.

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It's important to acknowledge this

1:40

because it may become a limitation.

1:43

There's two type of agents.

1:45

This agent can be a short acting agent

1:47

and they recommend that to do the FDG ptt

1:52

after 24 hours.

1:54

The long, long-acting agents

1:56

may have effect in the body over multiple days,

2:00

so it is recommended to wait 10 days.

2:03

Sometimes it's hard to schedule the patients as such,

2:06

but I would, I would say between seven

2:09

to 10 days, uh, would be ideal.

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Why? Because with this degree of intensity

2:16

in the bone marrow, you may be, uh, unable

2:20

to see if there are underlying lesions

2:23

and, uh, ultimately under a stage the patient.

2:28

Another thing that may help us, uh, differentiate, uh,

2:32

disease versus a physiological response

2:37

to these agents is the spleen.

2:41

The spleen is another organ that is part of the

2:44

reticular endothelial system.

2:46

It also becomes more metabolic

2:50

and response to these therapies.

2:53

And as we can see here on the bottom,

2:56

we see a diffuse uptick in the spleen.

2:58

I'm gonna show you in axial, and is the fierce.

3:02

There's no focal lesions,

3:04

but the degree of uptake is abnormal.

3:07

As we said at the beginning,

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the splenic uptake should be equal or less than the liver.

3:12

And in this case, we have the splenic uptake is greater than

3:15

the liver, but the uptick of the spleen

3:19

plus the findings on the bone marrow lead you to think

3:24

that this is just a physiological response

3:26

to the agent rather than disease.

3:29

Although sometimes in the certain cases like

3:32

lymphoma might be difficult to discern.

3:37

One of the things that can help us distinguish

3:40

abnormal asplenic uptake from, uh, lymphomas involvement,

3:44

for instance, from physiologic uh, metabolism, would be

3:49

look at the size of the spleen

3:52

as it is expected to be normal.

3:55

If this is only a response to these bone marrow

3:59

stimulating agents.